Regulation of helium atom higher harmonic emission and attosecond pulse angle in inhomogeneous fields

With the rapid advancements in modern science, the interaction between laser fields and matter has become a focal point of research in various disciplines. In this study, we investigate high-order harmonic generation (HHG) modulated by spatially inhomogeneous laser fields, using helium atoms as a model system. Two types of nanostructures – single gold-tip and double gold-tip configurations – are employed to generate spatially non-uniform laser fields that interact with the helium atoms. Our results reveal that the angular orientation of attosecond pulses is significantly influenced by the inhomogeneous parameters of the laser field. For a single gold-tip nanostructure, when the inhomogeneous parameter along the x-axis is fixed at 0.002 and the parameter along the y-axis is varied from 0.002 to 0.006, the angle between the attosecond pulse and the x-axis shifts from 129°to 139°. In the case of a double gold-tip nanostructure, with the same variation in the y-direction parameter and the x-direction parameter held constant at 0.002, the attosecond pulse angle decreases from 115°to 102°. Different from previous studies, this paper combines two nanostructures and focuses on how the angle of attosecond pulse is affected by heterogeneous parameters, revealing new properties of attosecond pulse dynamics. These findings demonstrate the critical role of spatial field inhomogeneity in tailoring attosecond pulse dynamics.